Vibrating apparatus for compacting molding sand

ABSTRACT

A vibrating apparatus for vibrating a flask to compact molding sand in the flask, including an elastically supported vibrating table on which a flask is placed and two unbalanced-weight-type motors mounted on the vibrating table at the sides of the flask for vibrating it by rotating the unbalanced weights of the motors. The axes of rotation of both motors are located on a horizontal line that substantially passes the centroid of the entire elastically supported vibrating apparatus, including the vibrating table, the two motors, the flask, and the molding sand in the flask. Further, both unbalanced weights of the motors are rotated at a speed in one direction.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a vibrating apparatus for vibrating aflask to compact molding sand in the flask, and in more detail, to animprovement of a vibrating apparatus for vibrating a flask to compactmolding sand in the flask that is provided with an elastically supportedvibrating table on which the flask is mounted and withunbalanced-weight-type vibrating motors mounted on the vibrating tablefor vibrating it by rotating the unbalanced weights of the motors.

[0003] 2. Description of the Prior Art

[0004] In conventional evaporative pattern casting, which uses moldingsand that includes no binder, or in conventional molding for producing aself-hardening mold, which uses molding sand that includes a smallamount of binders, a vibrating table is used for vibrating a flask tosatisfactorily and efficiently compact molding sand in the flask.

[0005] Such a vibrating table must cause the molding sand to movecircularly to satisfactorily and efficiently compact it when the flaskis vibrated. A vibrating device for circularly moving the molding sandto compact it is proposed in JP 10-828783, A. The vibrating device asshown in the Japanese patent gazette includes two unbalanced-weight-typemotors mounted on a vibrating table at the sides of a flask placed onthe vibrating table, with the axes of rotation of the motors beingarranged in parallel at the level of the centroid of the flask.

[0006] However, in the conventional vibrating device for compactingmolding sand, which is configured as described above, in fact the twounbalanced weights rotate out of phase, resulting in a phase differencebetween them. The phase difference causes a problem in that thevibrating table cannot move in a required circular motion since itoscillates laterally.

[0007] This invention has been conceived to overcome that problem. Itspurpose is to provide a vibrating apparatus for compacting molding sandthat can eliminate the oscillation of the vibrating table.

SUMMARY OF THE INVENTION

[0008] The vibrating apparatus of the present invention for vibrating aflask to compact molding sand in it includes an elastically supportedvibrating table on which the flask can be placed, and twounbalanced-weight-type motors mounted on the vibrating table forvibrating it by rotating the unbalanced weights of the motors. The twomotors are disposed above the vibrating table at the sides of the flask.The axes of rotation of the motors are located on a horizontal line thatsubstantially passes the centroid of the entire elastically supportedvibrating apparatus, including the vibrating table, the two motors, theflask, and molding sand in the flask. Further, the unbalanced weights ofthe motors are rotated at the same speed in one direction.

[0009] If there is a phase difference between the unbalanced weightswhen they are rotated at the same speed in one direction by the twomotors, the rotation moment of the two unbalanced weights is less thanthat when there is no phase difference, as shown in FIG. 1. In FIG. 1, Fdenotes the centrifugal force of one unbalanced weight, and L denotesthe radius of rotation of both weights. FIG. 2 shows the rotation momentof the unbalanced weights when the phase difference varies between them.If the common axis of rotation of the motors does not coincide with thecentroid of the entire vibrating apparatus, the apparatus wouldoscillate laterally. However, in the vibrating apparatus of the presentinvention the length of the arm of the rotation moment that accounts forthe lateral oscillation is zero. Therefore, the rotation moment thataccounts for the lateral oscillation will also be zero.

[0010] In one aspect of the invention, the vibrating apparatus includesmeans for adjusting the vertical position of the two motors to havetheir axes of rotation coincide with the centroid of the entirevibrating apparatus when the position of the centroid changes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 shows the rotation moment of two unbalanced weights whenthey are rotated at the same speed in one direction where they have aphase difference of 45°, 90°, 120°, 150°, 180°, 210°, 240°, or 270°.

[0012]FIG. 2 is a graph showing the rotation moment of the unbalancedweights when their phase difference varies.

[0013]FIG. 3 is a plan view of an embodiment of the vibrating apparatusof the invention.

[0014]FIG. 4 is a side view, partly in section, of the vibratingapparatus of FIG. 3.

[0015]FIG. 5a is a side new of another embodiment of the vibratingapparatus of the invention.

[0016]FIG. 5B is a plan view of another embodiment of the vibratingapparatus of the invention.

[0017]FIG. 6A is a side view of another embodiment of the vibratingapparatus of the invention, which has a mechanism for adjusting thevertical position of two motors.

[0018]FIG. 6B is a side view of another embodiment of the vibratingapparatus of the invention, which has a mechanism for adjusting thevertical position of the two motors.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Some preferred embodiments of the invention are now explained byreference to FIGS. 3-6. The same reference numbers denote the same orsimilar elements.

[0020] The first embodiment of the vibrating apparatus for compactingmolding sand is shown in FIGS. 3 and 4. The apparatus includes avibrating table 4 elastically supported on a machine base 2 by means ofcoil springs 3, 3 for carrying a flask 1 thereon. The apparatus alsoincludes two unbalanced-weight-type vibrating motors 6, 6 mounted on thevibrating table 4 for vibrating it by rotating a pair of unbalancedweights 5, 5 of the motors.

[0021] The two motors 6, 6 are disposed above the vibrating table 4 atthe sides of the flask 1, with their axes of rotation being on a line.Further, those axes substantially pass the centroid of the entirevibrating apparatus that is elastically mounted by means of the coilsprings 3, 3, including the vibrating table 4, the two vibrating motors6, 6, the flask 1, the molding sand in the flask 1, and an evaporativepattern M located in the flask. Further, the motors 6, 6 rotate theunbalanced weights at the same speed in one direction.

[0022] When the apparatus is operating, if the unbalanced weights 5, 5have a phase difference when rotated at the same speed in one directionby means of the vibrating motors 6, 6, the rotational motion of the twounbalanced weights is less than that when no phase difference occursbetween them, as described above. This rotation moment may cause thevibrating apparatus to oscillate laterally However, since in theapparatus of the invention the axes of rotation of the motors 6, 6substantially pass the centroid of the entire vibrating apparatus, thelength of the arm of the rotation moment that accounts for the lateraloscillation is zero. Thus no oscillation is caused.

[0023] Further, in an actual evaporative pattern molding, first, floorsand is compacted by linear vibrations Then, after a pattern is set in aflask, molding sand is moved circularly. The direction of the circularmotion of the molding sand may be changed during its compaction,depending on the direction that a hole of a pattern faces. When thedirection of the circular motion must be changed, just changing thedirection of the rotation of the motors does so.

[0024]FIG. 5A shows a second embodiment. If the apparatus of the firstembodiment is large, the motors 6, 6 cannot rotate at the same speed. Toovercome this problem, the motors 6, 6 are improved, as shown in FIG. 5AEach motor G has a toothed pulley 7 at one end of its output shaft. Arotary shaft 9 that has a toothed pulley 8 at each of its ends isdisposed under the vibrating table 4. The toothed pulleys 7, 7 of themotors 6, 6 are connected to the toothed pulleys 8, 8 of the rotaryshaft 9 by means of timing belts 10, 10 to rotate the motors 6, 6 at thesame speed in one direction. In this embodiment the machine base 2, coilsprings 3, 3, vibrating table 4, and unbalanced weights 5, 5 that areused in the first embodiment are also used.

[0025]FIG. 5B shows another embodiment to rotate the motors 6, 6 at thesame speed in one direction. Instead of the rotary shaft 9 coupled tothe motors 6, 6 as in FIG. 5A, a sensor 11 may be attached to one end ofthe output shaft of each motor 6 for detecting the phase differencebetween the two unbalanced weights. A phase controller 12 receives asignal representative of any phase difference from the sensors 11, 11attached to the output shafts of the motors and sends a synchronizingsignal to the motors so that they can rotate at the same speed in onedirection.

[0026]FIGS. 6A and 6B show the other embodiments, wherein a mechanism 13or 14 is mounted on the vibrating table 4 at each of the sides of flask1 to adjust the vertical location of the motors 6, 6. When, for example,the flask 1 is changed, the centroid of the entire vibrating apparatusmay change. In that case, the position of the axes of rotation of themotors 6, 6 must be changed so that it coincides with the centroid ofthe entire vibrating apparatus, to eliminate the lateral oscillation.

[0027] In FIG. 6A the mechanism 13 carries the motor 6 through a liftertable 15. The mechanism 13 includes a set of mated wedges 16, 17. Whenone of the wedges, i.e., 16 or 17, slides horizontally, the level of themotor is changed, i.e., the motor is moved to an upper or lowerposition.

[0028] In FIG 6B the mechanism 14 carries the motor 6 through a liftertable 15. The mechanism 14 includes threaded studs 19, 19 and nuts 20,21 threaded on them. When the nuts 20, 21 are moved upward or downward,the motor 6 is moved upward or downward.

[0029] Although the first embodiment describes compacting molding sandin an evaporative pattern casting, this invention can be also used tomold self-hardening sand, wherein the same operation is carried out, andthe same results can be obtained, as for the evaporative patterncasting.

[0030] For one skilled in the art, clearly some variations ormodifications can be made to the embodiments described above. The scopeof the invention includes such variations and modifications and is setforth in the attached claims.

What I claim is:
 1. A vibrating apparatus for vibrating a flask tocompact molding sand in the flask, comprising: an elastically supportedvibrating table on which a flask is placed; and twounbalanced-weight-type motors mounted on the vibrating table at sides ofthe flask for vibrating the vibrating table by rotating an unbalancedweight of each motor, with axes of rotation of the motors being locatedon a horizontal line that substantially passes a centroid of the entireelastically supported vibrating apparatus, including the vibratingtable, the two motors, the flask, and the molding sand in the flask, andwith the unbalanced weights of the motors being rotated at a speed inone direction.
 2. The apparatus of claim 1, wherein output shafts of thetwo motors are connected to each other through transmission means suchthat the output shafts rotate at a speed in one direction.
 3. Theapparatus of claim 1, further comprising a controller for controlling aphase difference between the unbalanced weights such that the outputshafts rotate at a speed in one direction.
 4. The apparatus of claim 1,further comprising means for adjusting a vertical location of themotors.
 5. The apparatus of claim 2, further comprising means foradjusting a vertical location of the motors.
 6. The apparatus of claim3, further comprising means for adjusting a vertical location of themotors.